129 (#183) ############################################ WOOLLEN YARN SPINNING tip of the spindles causes them to contract, and that when the carriage is freed from the outward draw it is drawn inwards by this contraction of the threads, aided by a conveyed tendency, until held by the jack-lever. The backing-off indirectly raises this jack-lever and thus frees the carriage for the run-in. (e) Backing-off must now be accomplished. This is effected by reversing the turning of the rim wheel B, which necessarily reverses the turning of the spindles. This is effected through the separate drive (usually rope, to ensure positive action) from the main mill shaft, through the two-grooved pulley F (Fig. 42), which, through toothed gearing, turns the toothed backing-off wheel c (Figs. 41 and 42) in the reverse direction. This wheel c (Fig. 41) forms a friction clutch with pulley 1. The arrival “in” of the carriage again giving half a revolution of the cam shaft of the mule withdraws the friction contact ; the half turn of the cam shaft on the arrival out of the carriage left it free under the control of the twist mechanism already described. Thus on the completion of the twisting with the carriage in the outward position the withholding catch is withdrawn, the backing-off wheel by friction engages I, and through it and the fast-speed rim B reverses the spindles and thus effects " backing-off." The further ” control of the motions must now pass to the mule carriage. () As backing-off takes place the faller-wires must come into action, the shaper-faller-wire sinking to the lowest position required for the stage arrived at in building up the spool and the counter-faller (weighted) rising, thus maintaining a constant tension on the threads or lengths backed-off. The control of this action rests with the tin-roller shaft, the reversing of this (from the headstock as already described) by means of a ratchet * 29